Safety shear pin for graders



1930. c. B. F-AVERTY 1,744,535

SAFETY SHEAR PIN FOR GRADERS .Filed Aug. 24, 1927 Ill" 5/ f l-lllllll Patented Jan. 21, 1930 CLYDE B. FAVERTY, OF HAMMOND, INDIANA SAFETY SHEAR PIN FOR GRADERS Application filed August 24, 1927. Serial No. 215,087.

My invention relates in general to road grading machinery.

It relates more particularly to a safety device for road graders, so designed that the safety factor may be accurately gauged.

A type of grader for performing various grading operations is shown in the co-pending application of Daniel C. Hinds, Serial No. 689,416, filed January 30, 1924. Graders of this type consist of a mold board secured to a wheeled frame, the frame and mold board being capable of a variety of adjustments to permit the performing of a relatively large number of grading operations by the same machine. These graders are always in danger of striking hidden obstacles of an immovable nature such as rocks and stumps, or becoming imbedded in a heavy clay or the like, or in other ways becoming subjected to such a strain on the parts as to result in serious breakage. They are generally drawn by a tractor, and of course to obtain flexibility of performance, a tractor with an excess amount of power is usually used, and the ex- 2 cess power may result in serious consequences to the equipment if really immovable obstacles are encountered.

The principal object of the present invention is to protect a road grader from hazards at of immovable obstacles.

Another object is to limit the tractive force applied to the grader to that which can be safely withstood by all the parts thereof.

Another object is to provide a safety pin adjustment having a definite yield point.

Another object is to insure uniformity in the load required to shear a safety pin.

Other objects and features of the invention will become apparent from a consideration of the following detailed description taken from the accompanying drawings wherein Fig. 1 is a fragmentary plan view of a grader tongue with one embodiment of my safety shear pin device applied thereto;

4 Fig. 2 is a side elevational view of partof the arrangement of Fig. 1, and

Fig. 3 is a sectional view along the line 3-3 of Fig. 2.

Reference may now be had to the accompanying drawings wherein like reference characters are employed to designate similar members throughout the several views.

The guiding tongue of a grader consists of an I-beam 10, having its web 11 disposed horizontally with the side flanges 12 and 13 vertical. The rear end of the tongue is con nected to the grader in any suitable manner, and the front end is adapted to be secured by means of a connector 14 to the draw bar 15 of a tractor. The tongue is provided with a coupling link 16 which is pivotally secured to the connector 14 and the connecting link is secured to the tongue in a manner to be described.

A channel-shaped binder plate 17 is secured by rivets 18 to the front end of the I- beam tongue. A rectangular aperture in the binder plate only slightly larger than cross section of the coupling link, permits the coupling link to be inserted therein in the manner shown. The web 11 of the I-beam is cut away to receive the portion of the coupling link which is secured through the aperture in the binder plate and this opening is also of a size to hold the coupling link in somewhat snug engagement.

Immediately to the rear of the opening in the web, a pair of clevis members 21 and 22 are riveted one to the top and the other to the bottom of the Web in the manner shown in Fig. 2. The clevis members are provided with offset portions 21 and 22 thereby forming an opening therebetween equal tothe thickness of the coupling link.

The offset portions of the clevis members are provided with hardened steel bushings 23 and 24 having flanges adapted to fit in counter-bored sections of the clevis members to prevent the bushings from being forced out of the apertures therein. A vertical pin re ceiving aperture in thecoupling link is pro vided having substantially the same diameter as the opening in the bushings. A shear pin 26 constructed of suitable material is then driven into the bushings and through the sign but I have shown it in the drawing as consisting of two oblong plates 27 and 28 secured intermediate their ends by a rivet 29 and spaced by a washer 31. The rear end of the coupler is provided with apertures adapted to cooperate with an aperture in the eX- tending end of the coupling link to receive a bolt 32 held in place by a nut 38. The connection is. loose at this point so that the bolt acts as a vertical pivot about which the connector can turn. The front end of the connector members are also provided with suitable apertures to cooperate with an aperture in the draw bar thus furnishing a second swivel connection. This is a conventional form of coupling, but has an advantage when employed with my safety shear pin arrangement.

It will be recalled that the coupling ink is in close engagement with the binder plate and web of the I-beam, as well as the offset portions of the clevis members, so that any rela" tive movement that might take place between the coupling link and these members is very slight. There is no wear therefore on the shear pin and no stress applied thereto excepta direct shearing stress. All movement incidental to the operation of the grader, and its connection to a tractor, is through the coupler, the pull being direct on the pin and the only stress applied thereto being such as to cause a shearing thereof, the load required to effect the shearing of the pin can be accurately gauged.

The bushings are hardened steel and act as shearing edges, and the coupling link can also be hardened to accentuate the shearing action.

My safety arrangement is adapted for use particularly with graders. It will be seen that it is comparatively simple to determine how great a load a given portion of the mechanism will hear. The load required to shear a pin of given diameter and constructed of a particular material can also be gauged with considerable accuracy. All that is necessary then, is to select a pin which will be sheared by the application of a load less than the load required to injure the parts of the grader which bears the working load. A fairly safe margin should of course be provided to offset unlooked for differences in material, workmanship or the like.

The shear pin of course can be modified to take care of different loads, either by changing its diameter, or by constructing it of different materials. hen the diameter is changed, it is of course necessary to change the bushings so that a tight fit will be obtained and no wearing movement take place between the connecting link and the shear pin.

The advantage of my invention is that the stress factor is reduced entirely to a matter of shearing, and the force required to shear a given member under identical conditions can be gauged with greater accuracy than when a variety of factors must be considered.

In assembling the shear pin joint, the pin which is made large enough to fit tightly into the bushings, is driven into place by means of a suitable tool. The flanges on the bushings of course prevent them from being forced out of the clevis members as the pin is driven into place. When the joint is assembled in this way it is bound to be tight so that no relative movement will take place between the pin and associated parts when the grader is in use.

For purposes of description I have made specific reference to certain details of my invention, but obviously I do not restrict myself thereto in the practice, but the invention is limited only by the scope of the appended claims.

\Vhat I claim as new and desire to secure by United States Letters Patent is 1. In a grader a guiding tongue consisting of an I-beam with its web in horizontal position, a channel support over the end thereof, a rectangular slot in the end of the web portion of the I-beam, a rectangular aperture in the channel support in line with said slot, a pair of clevis members secured to the web and projecting out over the slot, a link fitting snugly in said slot and between said clevis members, and a shear pin extending through the clevis members and link.

2. The arrangement defined in claim 1 with a hardened steel bushing in each one of the clevis members, the shear pin being tightly fitted into the bushings.

3. The arrangement defined in claim 1 with a hardened steel bushing in each one of the clevis members, the shear pin being tightly fitted into the bushings, and said bushings having flanges at the peripheral edges thereof to prevent their being displaced when the pin is driven into position.

4. In a power drawn grader, a tongue, a rectangular opening in the end thereof, a pair of clevis members secured to the tongue adjacent the opening, a coupling link in the opening and closely engaging the side edges thereof, a tool steel bushing in each clevis member, a tool steel bushing in'the coupling link in alignment with the bushings in the clevis members and abutting the same and a shear pin fitted snugly into said bushings so that all of the power for drawing said grader is applied through said pin, and the stress applied thereto is solely such as to shear the same.

In witness whereof, I hereunto subscribe my name this th day of July, 1927.

CLYDE B. FAVERTY. 

